The osteoinductive capacity of differently HCl-decalcified bone alloimplants

Three procedures to obtain bone inductive implants were tested heterotopically in 3-month-old allogeneic rats: 1) antigen-extracted HCl-decalcified at 4 degrees C, autolysed implant (AAA bone); 2) HCl-decalcified implant at 4 degrees C; 3) HCl-decalcified implant at room temperature. Each type of implant was either deep-frozen at -35 degrees C for at least 2 months or immediately freeze-dried. The bone inductive capacity of the differently HCl-decalcified cortical bone implant was evaluated at 2 months by isotopic strontium incorporation and by ash-weight measurements. Bone HCl-decalcification alone, either at 4 degrees C or at room temperature, gave a higher new bone yield than the freeze-dried AAA bone. The type or short-term preservation technique had no effect on the osteoinductive capacity of either of the differently treated implants, AAA bone expected.     

Thermal processing of homologous bone transplants for the bone bank as additional safety measure in AIDS prophylaxis]

Under the supposition that retrovirus is inactivated by heating at 56 degrees C, we explored what time was necessary to reach 65 degrees C as a central temperature in a femoral head by heating (14 femoral heads). We found that at a stove temperature of 85 degrees C and a femoral head volume of 81 ml the average central temperature was 66.1 degrees C after 1 hour. After 1.5 hours of heating a sufficient security should be guaranteed to avoid Aids-transmission by bone grafts.     

The effects of heat on the biological activity of recombinant human bone morphogenetic protein-2

This study was designed to investigate effects of heat on the bone-inducing activity of recombinant human bone morphogenetic protein (rhBMP)-2. rhBMP-2 samples were heated at 50, 70, 90, or 100°C for 15 min, or 1, 2, 4, or 8 h, or autoclaved at 120°C for 15 min. The bone-inducing activity of the rhBMP-2 before and after heating was assayed in in vivo and in vitro systems. For the in vivo assay, 5 μg rhBMP-2 samples were impregnated into porous collagen disks (6 mm in diameter, 1 mm thickness), freeze dried, and implanted into the back muscles of ddY mice. Three weeks later, the implant was harvested from the host and examined for ectopic new bone tissue by radiography. The new bone mass was quantified by single-energy X-ray absorptiometry. The in vitro activity of the rhBMP-2 was assayed by adding the BMP sample at a concentration of 100 ng/ml to cultures of MC3T3-E1 cells. After 48 h, the alkaline phosphatase activity was measured. After heating at 50° or 70°C, no significant reduction in bone-inducing activity was noted in either in vivo or in vitro assay systems unless the protein was exposed to sustained heat at 70°C for 8 h, based on in vitro assay data. However, heating above 90°C and for longer periods led to a decrease in the biological activity of the rhBMP-2 in a time- and temperature-dependent manner. rhBMP-2 was rendered inactive when exposed to temperatures at or in excess of 120°C.     

Heat shock-induced necrosis and apoptosis in osteoblasts.

Damage to bone tissue due to heat shock is one of the main causes of the failure of osseointegration at the bone-implant interface. To investigate the effect of heat shock on regeneration of bone tissue, osteoblasts were exposed to heat shock for 10 minutes at 42, 45, or 48 degrees C or kept at 37 degrees C as a control. After 10 minutes of heat shock, disruption of actin filaments was seen in the cells and the degree of disruption increased with the temperature. The cytoskeleton reassembled after a 12-hour incubation at 37 degrees C in the cells treated at 42 or 45 degrees C, but this reversible recovery did not occur in the cells treated at 48 degrees C. Flow cytometric analysis showed that heat shock at 48 degrees C increased the number of necrotic cells to 15-20% within minutes (p < 0.05 compared with 37 degrees C). Apoptosis, evidenced by annexin V staining, DNA laddering, and caspase 3 activation, started after 6-8 hours of incubation, reached a peak at 12 hours, and gradually declined (p<0.05). Pretreatment with the antioxidant N-acetyl-L-cysteine reduced the necrosis induced at 48 degrees C of heat shock by one-half (p<0.05) but had no significant effect on caspase 3 activation induced by heat shock, suggesting that reactive oxygen species were critical in heat shock-induced necrosis but not in apoptosis. Heat shock at 48 degrees C induced a sustained translocation of p53 into the nucleus and a sustained activation of c-jun N-terminal kinase, whereas that at 42 and 45 degrees C induced only transient p53 translocation and c-jun N-terminal kinase activation. These results suggest that the sustained activation of p53 and c-jun N-terminal kinase pathways may contribute to heat shock-induced apoptosis. On the other hand, heat shock protein 70 increased dramatically in the cells treated at 45 or 48 degrees C, suggesting that the protecting mechanism in the cells was also activated. Such protection was able to prevent apoptosis in cells treated at 45 degrees C but not in those treated at 48 degrees C.     

微波加热对脱钙骨基质诱导活性的影响

为了观察不同时间、温度微波加热后脱钙骨基质诱导活性的变化,作者以２４只成年纯种新西兰白兔为实验对象,随机分为２周（７只）、４周（７只）８周（５只）、１２周（５只）四个时间组。取兔左下肢胫骨用电锯锯成长度为０．８ｃｍ的移植骨６块,行微波加热。按不同时间、温度分为：３７℃、３０分钟组为１组;４５℃、３０分钟为Ⅱ且：６０℃、３０分钟为Ⅲ组;７５℃、３０分钟为Ⅳ组;７５℃、６０分钟为Ⅴ组;１００℃、３０分     

Acute right ventricular failure is caused by inadequate right ventricular hypothermia

The hypothesis of this study was that inadequate right ventricular hypothermia contributes to the right ventricular dysfunction occasionally observed after cardiac operations. Dogs were placed on cardiopulmonary bypass, and 60 minute periods of hypothermic myocardial ischemia were imposed. Left ventricular temperature was always maintained at 15 degrees C and right ventricular temperatures were maintained at 15 degrees C (Group I, n = 8), 25 degrees C (Group II, n = 8), and 35 degrees C (Group III, n = 8). These temperatures were produced by infusion of hypothermic crystalloid cardioplegic solution and appropriate topical cooling and heating of the left and right ventricles, respectively. Multiple indices of ventricular function were obtained 15, 30, 45, and 60 minutes after bypass and compared to prebypass control values. In all Group I animals (left ventricular temperature = 15 degrees C, right ventricular temperature = 15 degrees C), postischemic indices of right ventricular function were not different from control values (p = NS). In Group II (left ventricular temperature = 15 degrees C, right ventricular temperature = 25 degrees C), two animals died 30 and 45 minutes after bypass, respectively, of right ventricular failure. In the other six animals in Group II, all indices of right ventricular function were significantly reduced (p less than 0.05) except for right ventricular systolic pressure. In Group III (left ventricular temperature = 15 degrees C, right ventricular temperature = 35 degrees C), two animals could not be weaned from cardiopulmonary bypass because of right ventricular akinesia. Six animals were weaned from bypass, but two died 15 minutes, one died 30 minutes, and one 45 minutes after bypass. Two animals lived 60 minutes, but all indices of right ventricular function were decreased. Failure to maintain right ventricular temperatures below 25 degrees C during 1 hour of cardiac ischemia in the dog can result in fatal right ventricular failure.     

Adenosine and lidocaine: a new concept in nondepolarizing surgical myocardial arrest, protection, and preservation

OBJECTIVE: Depolarizing potassium cardioplegia has been increasingly linked to left ventricular dysfunction, arrhythmia, and microvascular damage. We tested a new polarizing normokalemic cardioplegic solution employing adenosine and lidocaine as the arresting, protecting, and preserving cardioprotective combination. Adenosine hyperpolarizes the myocyte by A1 receptor activation, and lidocaine blocks the sodium fast channels. METHODS: Isolated perfused rat hearts were switched from the working mode to the Langendorff (nonworking) mode and arrested for 30 minutes, 2 hours, or 4 hours with 200 micromol/L adenosine and 500 micromol/L lidocaine in Krebs-Henseleit buffer (10 mmol/L glucose, pH 7.7, at 37 degrees C) or modified St Thomas' Hospital solution no. 2, both delivered at 70 mm Hg and 37 degrees C (arrest temperature 22 degrees C to 35 degrees C). RESULTS: Adenosine and lidocaine hearts achieved faster mechanical arrest in (25 +/- 2 seconds, n = 23) compared with St Thomas' Hospital solution hearts (70 +/- 5 seconds, n = 24; P=.001). After 30 minutes of arrest, both groups developed comparable aortic flow at approximately 5 minutes of reperfusion. After 2 and 4 hours of arrest (cardioplegic solution delivered every 20 minutes for 2 minutes at 37 degrees C), only 50% (4 of 8) and 14% (1 of 7) of St Thomas' Hospital solution hearts recovered aortic flow, respectively. All adenosine and lidocaine hearts arrested for 2 hours (n = 7) and 4 hours (n = 9) recovered 70% to 80% of their prearrest aortic flows. Similarly, heart rate, systolic pressures, and rate-pressure products recovered to 85% to 100% and coronary flows recovered to 70% to 80% of prearrest values. Coronary vascular resistance during delivery of cardioplegic solution was significantly lower (P <.05) after 2 and 4 hours in hearts arrested with adenosine and lidocaine cardioplegic solution compared with hearts arrested with St Thomas' Hospital solution. CONCLUSIONS: We conclude that adenosine and lidocaine polarizing cardioplegic solution confers superior cardiac protection during arrest and recovery compared with hyperkalemic depolarizing St Thomas' Hospital cardioplegic solution.     

The osteoinductive capacity of differently HCI-decalcified bone alloimplants

Three procedures to obtain bone inductive implants were tested hetero-topically in 3-month-old allogeneic rats: 1) antigen-extracted HCl-decalci-fied at 4°C, autolysed implant (AAA bone); 2) HCl-decalcified implant at 4°C; 3) HCl-decalcified implant at room temperature. Each type of implant was either deep-frozen at-35°C for at least 2 months or immediately freeze-dried. The bone inductive capacity of the differently HCl-decalcified cortical bone implant was evaluated at 2 months by isotopic strontium incorporation and by ash-weight measurementsx. Bone HCl-decalcification alone, either at 4°C or at room temperature, gave a higher new bone yield than the freeze-dried AAA bone. The type or short-term preservation technique had no effect on the osteoinductive capacity of either of the differently treated implants, AAA bone expected.     

同种异体皮质骨板移植治疗股骨假体周围骨折

目的 评价同种异体皮质骨板移植治疗髋关节股骨假体周围骨折的临床治疗效果。方法 对7例髋关节置换术后股骨假体周围骨折患者应用深低温冷冻和环氧乙烷处理同种异体皮质骨板移植治疗股骨骨折。根据Harris评分,外周血T淋巴细胞亚群、抗体和免疫复合物检测、X线摄片以及核素骨显像评价其治疗效果。结果 患者未发生免疫排斥反应和感染,术后3、6、12、24个月Harris评分分别比术前平均增加21、32、40、40分。术后3个月骨折愈合,一部分移植骨板与宿主骨骨性连接,同位素骨显像骨板移植区放射性分布比对侧浓集。术后12个月,85％移植骨板与宿主骨融为一体,宿主股骨皮质厚度增加3～5mm,平均4．3mm,骨板放射性浓集进一步加深,15％移植骨板出现吸收现象。术后24个月,80％移植骨板重新塑形后恢复宿主股骨皮质骨密度,10％骨板表面吸收停止,股骨假体无松动。结论 深低温冷冻和环氧乙烷处理同种异体皮质骨板移植无菌、抗原性弱、生物相容性好,移植骨板能够维持骨折和假体稳定性,增加股骨局部骨量储备,避免再次手术取出金属内置物,是用来治疗股骨假体周围骨折较理想的方法之一。     

热籽感应加温体内外升温情况及其对荷瘤大鼠免疫功能的影响

目的评估热籽在交变磁场中体外升温及其对荷瘤大鼠加温治疗效果和对免疫功能的影响。方法监测居里点分别为57℃及70℃热籽体外升温情况。40只接种Walker-256肿瘤细胞的Wistar大鼠,随机分为C组（空白对照组）10只,M组（磁场对照组）5只,T组（热籽对照组）5只,加温治疗H1组10只、H2组10只。H1组：瘤内植入2颗居里点57℃热籽,持续30min;H2组：2颗居里点70℃热籽,持续6min。加温治疗后9天各组均处死5只大鼠测其肿瘤体积及质量,剩余H1、H2组及C组大鼠检测外周血T淋巴细胞亚群。结果热籽体外升温可达到其居里点温度。热疗后肿瘤体积中位数H2组0．50cm^3（0．00～26．54）明显小于M组36．18cm^3（0．96～39．90）（Z=2．21,P=0．032）,肿瘤质量中位数H1组0．96g（0．00～21．18）、H2组0．41g（0．00—23．40）明显小于M组31．45g（1．09—36．09）（二者均为Z=2．21,P=0．032）。外周血T淋巴细胞亚群CD4^＋H1组（22．39±5．27）％、H2组（24．76±5．19）％明显高于C组（12．07±4．45）％（P=0．01,0．003）,CD8^＋ H2组（19．58±4．63）％明显高于C组（12．72±3．96）％（P=0．04）。结论热籽在交变磁场中能达到适宜的温度,其感应加温治疗对荷瘤大鼠肿瘤生长有一定的抑制作用,能提高免疫功能。     

In vitro bactericidal effect of a modified thermal Nitinol electrode

PURPOSE: A standard electrode surgical generator connected to a Nitinol coil was used in vitro to evaluate whether the generated electromagnetic energy had any bactericidal effect on Escherichia coli. MATERIALS AND METHODS: The ATCC 259222 E. coli strain was used. We mixed 135 mL of a 1.5% non-nutritive agar with 15 mL of a 10(6) CFU/mL inoculum and transferred it to gas-sterilized plastic containers lined with aluminium foil. A 22F cylindrical shape was cut from the center of the agar, and a Nitinol coil was placed in that space and connected to a standard electrode surgical generator. Electrical energy was then applied from 5 to 25 V at 5-V increments. Temperatures were measured with two thermocouples placed in the middle and periphery of each agar. The treatment was stopped when the temperature at the middle thermometer reached 50 degrees C. The control group was not treated and was embedded in a water bath at 45 degrees C. Three 3 x 7-mm pieces were sliced from the inner to the outer part of the agar and processed, and colony counts were performed. RESULTS: We observed statistically significant deleterious effects on E. coli in all three zones when the treatment voltage was 15 and 20. When the potential was raised to 25 V, we observed a significant result only in the core zone. The treatment duration was 50 minutes for 5 and 10 V, 45 minutes for 15 V, 15 minutes for 20 V, and 10 minutes for 25 V. CONCLUSION: The bactericidal effect was mainly in the central area, decreasing linearly toward the periphery, and was related to the temperature reached during activation of the electrical generator. These results were disappointing with regard to the utility of Nitinol stents to treat bacterial prostatitis.     

Smart intramedullary rod for correction of pediatric bone deformity: a preliminary study

We were interested in determining if a smart intramedullary rod made of nitinol shape-memory alloy is capable of correcting deformed immature long bones. Because of limitations in our study design the process was reversed in that we examined the smart rod's ability to create a deformity rather than to correct one. Smart rods of different lengths and diameters were heat-treated to resume a radius of curvature of 30 to 110 mm. The low and high temperature phases of the smart rods were set, respectively, at 0 degrees C to 4 degrees C and 36 degrees C to 38 degrees C. The preshaped smart intramedullary rods were implanted in the cooled martensite phase in the medullary canal of the tibia in eight rabbits, where they restored their austenite form, causing a continuous bending force. On a weekly basis anteroposterior and lateral radiographs of the surgically treated tibia and the contralateral tibia were obtained for comparison. Rabbits were euthanized 6 weeks after surgery and computed tomography scans of both tibias were used for image analysis. Smart rods with a larger radius of curvature showed only minimal signs of remodeling; however, rods with a radius of curvature of 50 and 70 mm generated enough force history to create bone remodeling and deformation. The amount of bone deformation was highly magnified when unicortical corticotomy on the tension side was done. Based on this preliminary study the technology of the smart intramedullary rod may provide a valuable alternative method to correct pediatric skeletal deformities.     

Effect of freeze time during renal cryoablation: a swine model

BACKGROUND AND PURPOSE: Cryotherapy provides a minimally invasive treatment for small renal tumors via an open, percutaneous, or laparoscopic approach. We sought to determine the most appropriate duration of freezing and the number of probes necessary to produce cell death without concomitant morbidity. MATERIALS AND METHODS: Nine domestic female pigs were divided into three groups of three animals each. Each group underwent a single freeze cycle with a commercially available cryotherapy device with 3.4-mm probes: group 1 for 5 minutes, group 2 for 10 minutes, and group 3 for 15 minutes. The right kidney was treated with a single probe, the left with a double probe. Animals were permitted to survive for an average of 4.8 days (range 4-7 days), after which the kidneys were harvested. A single pathologist examined the kidneys for gross and histologic changes. Evidence of complications (fistula, bleeding, bowel injury) was documented at the time of necropsy. RESULTS: For group 1, the temperature obtained with a single probe 5, 10, 15, and 20 mm from the probe was -57 degrees C, 3 degrees C, 25 degrees C, and 33 degrees C, respectively; for group 2 -85 degrees C, -37 degrees C, -2 degrees C, and 25 degrees C; and for group 3 -10 degrees C, -45 degrees C, -20 degrees C, and 6 degrees C. For group 1, the temperature obtained with a double probe at 5, 10, 15, and 20 mm from each probe was -65 degrees C, 0 degrees C, 20 degrees C, and 30 degrees C, respectively; for group 2 -72 degrees C, -25 degrees C, 5 degrees C, 25 degrees C; and for Group 3 -82 degrees C, -30 degrees C, -12 degrees C, 13 degrees C. Complete necrosis was seen 5 mm from the cryoprobe within each group, but only in groups 2 and 3 did necrosis extend 10 mm or beyond the probes when utilizing either single or double probes. The maximum diameter of consistent necrosis was 35 to 40 mm in the animals in group 3 treated with a double probe. Bleeding and renal fracture were the two most common complications. CONCLUSIONS: A 5-minute freeze appears to be inadequate to cause tissue necrosis and is associated with excessive bleeding at the time of the procedure, whereas the 15-minute freeze produces consistent necrosis but is associated with renal fracture. In this animal model, the 10-minute freeze with the single or double probe configuration appears optimal to produce necrosis without complications.     

Second prize: simple method for achieving renal parenchymal hypothermia for pure laparoscopic partial nephrectomy

PURPOSE: We describe the development of an innovative device and simple technique for achieving renal parenchymal hypothermia during temporary renal-vascular occlusion for pure laparoscopic partial nephrectomy. MATERIALS AND METHODS: The experiment was conceived in four phases: phase 1: design, manufacture, and testing of the cooling coil; phase 2: proof of concept in nonsurvival porcine surgery; phase 3: experimental porcine survival surgery; and phase 4: human trials. RESULTS: Phase 1 testing confirmed that the coil cooled adequately. During phase 2, the average time required for the renal parenchyma to cool to 15 degrees C was 10.7 minutes, providing an average hypothermic window (15 degrees -24 degrees C) of 30.3 minutes. When recooling was required (parenchymal temperature 24 degrees C), temperatures returned to below 15 degrees C in 3 minutes. The core body temperature dropped an average of 1.48 degrees C. Phase 3 demonstrated an average parenchymal temperature of 11.7 degrees C after a mean cooling time of 9.3 minutes. Temperatures remained below 24 degrees C for an average of 26.7 minutes. Recooling took 3 minutes, and in no procedure did the renal parenchyma temperatures ever return to >24 degrees C prior to reperfusion. The core body temperature dropped an average of 2.20 degrees C. At 48 hours after reperfusion, selective renal-vein blood was obtained for creatinine assay, and the kidneys were harvested. Creatinine results were not statistically different in the treated and control groups. Blinded pathologic analysis confirmed a protective effect using our cooling system. CONCLUSION: Our method is simple, effective, and reproducible.     

术中微波原位加热与辅助化疗治疗恶性骨肿瘤的随诊报告

四肢骨肿瘤保肢手术各有其优缺点。为探讨新的治疗方法，１９８０年７月～１９９４年１２月，作者对２５例骨肿瘤患者进行了微波原位加热与辅助化疗的综合治疗。其中男１５例，女１０例。年龄：１０～４６岁，平均２５．８岁。肿瘤部位：股骨下端１６例，胫骨上端５例，股骨干２例，髂骨２例。肿瘤类型：骨肉瘤１６例，皮质旁骨肉瘤４例，软骨肉瘤３例，平滑肌肉瘤２例；肿瘤分期：Ⅱｂ１７例，Ⅱａ５例，Ⅲｂ３例。加热温度５０℃，持续时间１５分钟，分野照射，多点测温。本组２５例术后平均随访５７个月。５年生存率为７０．４９％，１０年生存率为５４．８３％。术后２１例综合功能（Ｅｎｎｅｋｉｎｇ标准）＞１５分。结果提示本方法无需截骨和内固定，可以准确控制温度和时间，对骨组织损伤小，有利于术后骨组织重建，远期并发症少，手术操作简单，推广性强。     

Rapid body cooling by cold fluid infusion prolongs survival time during uncontrolled hemorrhagic shock in pigs

OBJECTIVE: The purpose of this study was to examine whether cold fluid infusion could rapidly decrease the core temperature and prolong survival during uncontrolled hemorrhagic shock in pigs. METHODS: Fourteen pigs under light halothane anesthesia and spontaneous breathing underwent initial blood withdrawal of 25 mL/kg over 15 minutes, followed by uncontrolled hemorrhage (5-mm aortotomy). Immediately after the aortotomy, the pigs were randomized to receive 500 mL lactated Ringer's solution at either 4 degrees C (group 1, n = 7) or 37 degrees C (group 2, n = 7) over 20 minutes through the internal jugular vein and observed until their death or for a maximum of 240 minutes. RESULTS: The pulmonary artery temperature of group 1 decreased to 35.5 degrees +/- 0.3 degrees C after the infusion, then remained at 35.5 degrees C during the observation period. Pulmonary artery temperature values of group 2 remained at around 37.5 degrees C throughout the experiment. The mean survival time was 220 +/- 45 minutes in group 1 versus 136 +/- 64 minutes in group 2 (p < 0.05, life table analysis). The additional intraperitoneal blood loss of group 1 was similar to that of group 2 (9 +/- 4 g/kg vs. 10 +/- 5 g/kg). CONCLUSION: In lightly anesthetized pigs during uncontrolled hemorrhagic shock, infusion with 4 degrees C lactated Ringer's solution (which seems to be feasible in the clinical setting) decreases the core temperature rapidly and prolongs survival.     

Endothelial dysfunction caused by University of Wisconsin preservation solution in the rat heart. The importance of temperature.

The superiority of the University of Wisconsin solution over routinely used crystalloid cardioplegic solutions for myocardial preservation has been demonstrated in animal studies. We have investigated the effect of the University of Wisconsin solution at different temperatures on endothelial function by examining its influence on 5-hydroxytryptamine- and nitroglycerin-induced increase in coronary flow in the isolated rat heart. Thirty-eight rat hearts were perfused on a modified Langendorff preparation. In the control experiments, there was no significant difference in the percentage increase in coronary flow induced by 5-hydroxytryptamine and nitroglycerin after 30 minutes of perfusion with Krebs-Henseleit buffer (n = 6). Continuous infusion of the University of Wisconsin solution for 30 minutes at 4 degrees C or at 10 degrees C did not alter the 5-hydroxytryptamine or nitroglycerin response. However, infusion at 15 degrees C reduced the 5-hydroxytryptamine-induced vasodilation, while at 20 degrees C the 5-hydroxytryptamine response was converted to vasoconstriction without a significant change in nitroglycerin effect (15 degrees C, 5-hydroxytryptamine, before: 30.2% +/- 1.5%, after: 6.0% +/- 1.0%, nitroglycerin, before: 28.8% +/- 1.3%, after: 31.2% +/- 1.8%; 20 degrees C, 5-hydroxytryptamine, before: 32.2% +/- 2.5%, after: -23.8% +/- 3.6%, nitroglycerin, before: 30.3% +/- 1.9%, after: 33.5% +/- 1.7%). Coronary vascular resistance in the control experiments rose from 55.0 +/- 2.5 cm H2O/ml/gm/min to 58.4 +/- 2.3 cm H2O/ml/gm/min (p = not significant). The increase after University of Wisconsin solution infusion at 4 degrees C and at 10 degrees C was similarly not significant. Coronary vascular resistance increased significantly following infusion of University of Wisconsin solution at 15 degrees C (p < 0.001) or at 20 degrees C (p < 0.01). We conclude that University of Wisconsin solution produces temperature-dependent endothelial dysfunction in the isolated rat heart.     

Cerebral blood flow changes during localized hyperthermia.

Hyperthermia is becoming a potent therapeutic method for malignant brain tumors, either alone or in combination with radiation therapy. The heat response of organized tissues includes other factors besides the inherent cellular thermosensitivity, that is, tissue pH, PaO2, and nutrient supply, all of which are largely influenced by the tissue blood flow. In this study, the regional cerebral blood flow (rCBF) changes in 15 Japanese normal monkey brains during interstitial microwave hyperthermia were investigated by the hydrogen clearance method. Under general anesthesia and controlled respiration, a parieto-occipital craniectomy, 4 x 4 cm, was performed. A microwave antenna was inserted into the brain to a depth of 2.0 cm, and the brain tissue was heated with 2450 MHz microwave irradiation. The intracerebral temperatures and rCBF were measured in the white matter 1 cm from the brain surface. During hyperthermia, the rCBF linearly increased at a rate of 10% per 1 degrees C temperature rise. Heating at 42 degrees C for 180 minutes resulted in a constant increase in rCBF. The perfusion rate returned to the control levels after the termination of heating. Above 45 degrees C, the rCBF transiently increased and then started to decline during heating. No consistent results were obtained with heating at 43 degrees C. These results show that normal monkey brain tissues respond to hyperthermia by an rCBF increase as long as the threshold values of tissue temperature (43 degrees C) and exposure time (40-60 minutes) are not exceeded. Excessive heating may lead to irreversible damages to normal tissue and vasculature.     

Thermological study of drilling bone tissue with a high-speed drill

OBJECTIVE: To perform a detailed quantitative analysis of the effect of intermittent drilling and irrigation to lower the temperature during high-speed drilling. METHODS: We examined the thermal changes for 15 bone flaps while drilling a 7- x 7-mm area for 18 seconds and a specific point for 9 seconds, under the following conditions: continuous or intermittent drilling; with a fluted steel or a diamond ball cutter; without or with irrigation, with room temperature or cold (8 degrees C) Ringer solution. RESULTS: The maximum temperature during continuous drilling with a diamond cutter (or steel cutter) was 82.4 +/- 1.3 degrees C (55.2 +/- 1.0 degrees C) without irrigation, 42.5 +/- 1.2 degrees C (35.4 +/- 0.9 degrees C) with room temperature Ringer irrigation, and 22.5 +/- 1.4 degrees C (21.6 +/- 0.3 degrees C) with cold Ringer irrigation, whereas that during intermittent drilling was 66.1 +/- 1.2 degrees C (35.6 +/- 0.8 degrees C), 35.0 +/- 0.8 degrees C (25.4 +/- 0.7 degrees C), and 21.5 +/- 0.6 degrees C (21.8 +/- 0.4 degrees C), respectively. During continuous drilling of a specific point, the radius of the concentric isothermal line for 43 degrees C (thermal threshold for neurons) was 3.6 +/- 0.8 mm with a steel cutter, and it was 8.1 +/- 0.3 mm with a diamond cutter. The radius was 4.2 +/- 0.8 mm during intermittent drilling with a diamond cutter, and it was 4.0 +/- 0.1 mm during continuous drilling with room temperature Ringer irrigation. Intermittent drilling with cold Ringer irrigation kept the temperature, even at the center of the drilled area, below 20 degrees C. CONCLUSION: Intentional intermittent drilling with irrigation reduces temperature elevation and its expansion. These procedures are necessary for safe drilling, especially with a diamond burr. Although cold irrigation can minimize temperature elevation, its substantial effect on nerves or other structures needs to be elucidated.     

Flow characteristics of acrylic bone cements

Flow properties of Simplex, Zimmer Regular, Zimmer LVC, and Sulfix bone cements were measured as functions of time between two and five minutes after mixing. The mass flowrates measured for Zimmer Regular and Simplex were quite similar in the temperature range of 20.0 degrees -23.3 degrees. At 18.3 degrees Simplex had approximately double the flowrate of Zimmer Regular two minutes after mixing. The flowrate for LVC was approximately four times that measured for Zimmer Regular at 20.0 degrees. Sulfix displayed the greatest sensitivity of flowrate with temperature; at 18.3 degrees its flow characteristics were similar to those of LVC, and at 23.3 degrees it behaved more like Simplex and Zimmer Regular. All cements demonstrated substantial relative increases in flowrates with only slight increases in pressure; Sulfix was the most pressure sensitive. Set times for Zimmer, LVC, and Sulfix were virtually identical, ranging from a mean of 11 minutes (at 18.3 degrees) to 7.5 minutes (at 23.3 degrees). Simplex had considerably longer set times, averaging 15.8 minutes (at 18.3 degrees) and 9.4 minutes (at 23.3 degrees). Although Simplex demonstrated the greatest sensitivity of set time with temperature (almost double that measured for the other 3 cements), it did not show the greatest sensitivity of flowrate with temperature.